trello_json_to_csv.py

import csv
import json
from collections import defaultdict

with open('trello_export.json', "r") as f:
    json_data = f.read()
data = json.loads(json_data)

cards = data['cards']
actions = data['actions']
lists = [l for l in data['lists'] if not l["closed"]]

cards_by_list = defaultdict(list)
for card in cards:
    cards_by_list[card["idList"]].append(card)

print "Loaded {} cards into {} lists".format(len(cards), len(cards_by_list))

with open('trello_export.csv', 'wb') as csvfile:
    writer = csv.writer(csvfile)

    list_ids = cards_by_list.keys()
    header_row = [l["name"] for l in lists]
    writer.writerow(header_row)

    while(True):
        row = []
        empty = 0
        for l in lists:
            if cards_by_list[l["id"]]:
                row.append(cards_by_list[l["id"]].pop()["name"])
            else:
                empty += 1
                row.append("")
        writer.writerow(row)

        if empty == len(list_ids):
            break

print "Done"